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MOA-2010-BLG-073L: An M-dwarf with a Substellar Companion at the Planet/Brown Dwarf Boundary

Street, R. A. and Kane, S. R. (2013) MOA-2010-BLG-073L: An M-dwarf with a Substellar Companion at the Planet/Brown Dwarf Boundary. Astrophysical Journal, 763 (1). Art. No. 67. ISSN 0004-637X.

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We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales >200 days. Its dereddened color, (V – I)_(S,0), is 1.221 ± 0.051 mag, and from our lens model we derive a source radius of 14.7 ± 1.3 R_☉, suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 ± 0.0006. The Einstein crossing time of the event, t_E = 44.3 ± 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, D_L = 2.8 ± 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with M_(L,1) = 0.16 ± 0.03 M_☉, while the companion has M_(L,2) = 11.0 ± 2.0 M_J, putting it in the boundary zone between planets and brown dwarfs.

Item Type:Article
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URLURL TypeDescription
Street, R. A.0000-0001-6279-0552
Kane, S. R.0000-0002-7084-0529
Additional Information:© 2013 American Astronomical Society. Received 2012 September 12; accepted 2012 November 3; published 2013 January 8. R.A.S. is grateful to the Chungbuk University group and especially to C. Han and J.-Y. Choi for their advice and hospitality in Korea, where much of this work was completed. R.A.S. also expresses appreciation for Y. Tsapras, K. Horne, M. Hundertmark, S. Dong, and P. Fouqué for many useful discussions. K.A., D.M.B., M.D., K.H., M.H., C.L., C.S., R.A.S., and Y.T. thank the Qatar Foundation for support from QNRF grant NPRP-09-476-1-078. Work by C. Han was supported by the Creative Research Initiative Program (2009-0081561) of the National Research Foundation of Korea. C.S. received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 268421. The OGLE project has received funding from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 246678 to AU. This publication makes use of data products from the Exoplanet Encyclopeida and the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. M.O.A. acknowledges funding JSPS20340052, JSPS22403003, and JSPS19340058. T.C.H. gratefully acknowledges financial support from the Korea Research Council for Fundamental Science and Technology (KRCF) through the Young Research Scientist Fellowship Program. C.U.L. and T.C.H. acknowledge financial support from KASI (Korea Astronomy and Space Science Institute) grant number 2012-1-410-02. D.R. (boursier FRIA), F.F. (boursier ARC), and J. Surdej acknowledge support from the Communauté francaise de Belgique-Actions de recherche concertées-Académie universitaire Wallonie-Europe. A. Gould acknowledges support from NSF AST-1103471. B. S. Gaudi, A. Gould, and R. W. Pogge acknowledge support from NASA grant NNX12AB99G. Work by J. C. Yee is supported by a National Science Foundation Graduate Research Fellowship under grant No. 2009068160. S.D. is supported through a Ralph E. and Doris M. Hansmann Membership at the IAS and NSF grant AST-0807444. Facilities: FTN, Liverpool:2m, CTIO:1.3m, MtCanopus:1m, Elizabeth, Danish 1.54m Telescope
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Qatar National Research FoundationNPRP-09-476-1-078
National Research Foundation of Korea2009-0081561
European Research Council (ERC)268421
European Research Council (ERC)246678
Japan Society for the Promotion of Science (JSPS)JSPS20340052
Japan Society for the Promotion of Science (JSPS)JSPS22403003
Japan Society for the Promotion of Science (JSPS)JSPS19340058
Korea Research Council for Fundamental Science and Technology (KRCF) Young Scientist Research Fellowship ProgramUNSPECIFIED
Korea Astronomy and Space Science Institute (KASI)2012-1-410-02
Communauté française de Belgique – Actions de recherche concertées – Académie universitaire Wallonie-EuropeUNSPECIFIED
NSF Graduate Research Fellowship2009068160
Subject Keywords:brown dwarfs; gravitational lensing: micro; planetary systems; planets and satellites: formation; planets and satellites: general; techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20130215-151001529
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Official Citation:MOA-2010-BLG-073L: An M-dwarf with a Substellar Companion at the Planet/Brown Dwarf Boundary R. A. Street et al. 2013 ApJ 763 67
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36968
Deposited By: Ruth Sustaita
Deposited On:15 Feb 2013 23:46
Last Modified:09 Mar 2020 13:19

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